Cell and gene therapies must be tested for sterility, stability, purity and potency. Testing cellular and gene therapies is challenging. These therapies are generally collected from a single person so the quantity of material available to test is limited. They are generally transfused immediately after they are produced so there is a very limited amount of time to complete the assays. Many of these therapies are complex cells that have multiple functions. The cell functions that are critical to the clinical effectiveness of these therapies is often not known. Traditionally analytic assays such as flow cytometery, ELISA, ELISPOT and cell culture assays have been used to analyze cellular and gene therapies. While these assays have proven to be very useful, the number of factors that can be analyzed with these assays is limited. We have been investigating the use of gene and micro RNA expression analysis for the analysis of cellular therapies. These assays can require the use of only a small quantity of cells and can be used to test up to 36,000 factors at one time. We have been testing the ability of global gene and micro RNA expression profiling to determine the utility of these assays for assessing the stability, purity and potency of cellular therapies. We have shown that gene expression profiling can detect changes in stored cells and detect differences between peripheral blood leukocytes (T cells, B cells and monocytes) and hematopoietic stem cells. Gene expression profiling has also been able to detect differences between immature and mature DCs and has been useful for comparing mature DCs produced using different combinations of maturation agents. We are also investigating the use of gene and micro RNA expression profiles to assess the potency of hematopoietic stem cells. Preliminary results suggest that both assays can distinguish peripheral blood stem cells mobilized with different agents and isolated with different antibodies.